[ck2]

Except I've never, ever heard of this used to solve a crime.

Definitely never used in court or we'd hear about it but they probably wouldn't risk the constitutionality of that.

So they are just collecting it for the sake of spying on everyone. Lovely.

[anigbrowl]

Just because you haven't heard of it doesn't mean it doesn't happen. Here's a case from 1970: http://scholar.google.com/scholar_case?case=1776184466461190...

You'll notice that early on, it mentions Ex Parte Jackson, an 1878 case which established that the contents of mail are protected by the Fourth Amendment, but that the outward form is not. Mail 'metadata' has always been fair game, just as it would be fair for a police officer to observe your comings and goings on the street without any need for a warrant.

Then there's the Postal Inspection Service, which is the law enforcement agency that specializes in mail fraud (perhaps you've heard of that?) and which predates the founding of the USA.

I don't mean to be rude, but the fact that you've 'never, ever heard of' something doesn't mean anything special. You don't strike me as terribly well-informed.

[tokenadult]

Except I've never, ever heard of this used to solve a crime.

Reading the fine submitted article would solve that problem.

[swamp40]

...by examining information from the front and back images of 60 pieces of mail scanned immediately before and after the tainted letters sent to Mr. Obama and Mr. Bloomberg showing return addresses near her [Ms. Richardson's] home.

Those are some powerful tools for investigators.